KHedges

This seems like a really silly question, but I've replaced the off-white 2-pin brake light switch multiple times and symptoms persist. Is this black switch also a brake light switch?

It's a 1999 A6 Avant Quattro 2.8L automatic, in case any of those details are relevant.


Photo of two switch type devices at the top of the brake pedal. One is ivory color with a purple 3-pin connector, the other is black with a black connector that could have 4 pins.

All the instructions I've seen just say "the brake light switch" and I presumed there was only one. Are both of these brake light switches? If so, I probably need to replace the black one too.

Symptoms: Occasional brake warning light on dash with frantic beeping (not ABS, the same light as when my parking brake is on) and occasional rear brake lights staying on. (It drained my battery overnight.)

Also, if both are brake light switches, does the black one look like the plunger click kind that can't be readjusted or the screw in adjustable kind?

Thanks!

georgeb944

The white switch is component F, which is the brake light switch. The black switch is component F47, which is the brake pedal switch.

The wiring diagram for the ABS system shows both being used for the ABS. The wiring diagram for the cruise control system also shows both being used for the cruise system.

I have attached pdfs of the diagrams for both.

Harleyguy

Not 100% sure but I believe that one is the brake light switch and the other is part of the interlock for the transmission selector lever. (depress brake pedal to shift out of park). I believe the off-white is the interlock and the black is the actual switch for the lights. Based on your photo I would say it is adjustable; looks as if the plunger is threaded. The off-white is also adjustable per the threads on the switch housing. Try Google-ing the subject and see what hits come up. You might find a Youtube video or other source of info on this. The Bently manual may help as well.

KHedges

Thank you for the information. Do you know if the brake pedal switch goes bad too? I'll study the diagrams after I catch up on sleep. (Long night shift + car issue...)

K

KHedges

So I looked at your diagrams, and I'm not familiar with wiring diagrams so all I took away was that both these switches are necessary and the other is called a brake pedal switch. Unfortunately, Google wasn't helpful because I found a couple of good YouTube videos for R/R that switch but no way to buy a new one.

For my model year, the new parts suppliers all say it only has the ivory brake light switch. The black brake pedal switch is not listed for my model year, only 2002 and later. So I don't know if that means my car takes a slightly different switch that is out of production and I should get a used one, or there's a parts application database glitch.

https://www.ecstuning.com/b-genuine-.../1k2945511rdw/

https://parts.capitolvolkswagen.com/...945511RDW.html

georgeb944

I don't have any additional information on your car. You might want to take a look at the pedal area where the switch(es) should be and the part number should be on the switch itself.

KHedges

So I finally pinged my friend, who recognized it because it was a pain to track down when his wife's Passat had the same issue. It's also part of the Cruise Control system, with a vacuum line connection as well as electrical. Despite the wiring diagram calling it a "brake pedal switch" the official name is the "deactivation switch" or "cruise control valve". Hopefully this will fix my problems, and the cruise control will work again. (Not a priority for my local driving, but when it's ready for a road trip, it could be nice. We've resoldered the relay, and eventually I might get a new stalk switch.)


Cruise Control valve aka Deactivation switch. Similar pricing at most online German parts stores.